Inkjet ink and primer fluid set

ABSTRACT

The present disclosure provides an inkjet ink and primer fluid set containing an aqueous primer composition, an aqueous white inkjet ink, and aqueous non-white colored inkjet inks. The aqueous primer composition forms a coating on a print substrate. This fluid set is particularly suitable for printing on non-porous plastic substrate.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119 from U.S.Provisional Application Ser. No. 62/949,783, filed Dec. 18, 2019.

BACKGROUND OF THE DISCLOSURE

This disclosure pertains to an inkjet ink and primer fluid setcontaining an aqueous primer composition, an aqueous white inkjet ink,and aqueous non-white colored inkjet inks. The aqueous primercomposition forms a coating on a print substrate. This fluid set isparticularly suitable for printing on non-porous plastic substrate.

Inkjet printing is a non-impact digital printing process in whichdroplets of ink are deposited on a substrate, such as paper, to form thedesired image. Inkjet printers are equipped with an ink set which, forfull color printing, typically comprises a cyan, magenta and yellow ink(CMY). An ink set also typically comprises a black ink (CMYK) with theblack ink being the most common ink.

Inkjet printing is becoming increasingly important for markets otherthan conventional desktop printing for small office/home office. Digitalprinting methods have gained popularity in textiles, commercial andpackaging printing and offer a number of potential benefits overconventional printing methods such as screen printing, offset printing,flexo and gravure printing. Inkjet digital printing eliminates the setupexpense associated with screen and plate preparation and can potentiallyenable cost effective short run production. Inkjet printing furthermoreallows visual effects such as tonal gradients and infinite patternrepeat sizes that cannot be practically achieved with a screen and otheranalog printing processes.

Aqueous inkjet ink has grown rapidly in packaging application in recentyears, because it is a digital technology with less environmental impactcompared to UV and solvent digital inks. Non-porous plastics, includingboth flexible plastic films and rigid plastics, are commonmedia/substrate for packaging applications. The surfaces of theseplastics are non-liquid absorbing and hydrophobic by nature, and imposemany performance challenges for aqueous pigmented inks. Among them a keychallenge is poor image quality due to slow setting of the ink drops asthe results of non-ink absorbing of the printing surface and lowtemperature drying to avoid plastic substrate distortion. Slow fixationand drying of the ink drops can lead to blurry image and inter-colorbleed, which worsen especially when printing at high speed.

To improve print image quality on a hydrophobic substrate, a commonapproach is to coat the hydrophobic surface with a primer orpretreatment fluid. US Patent Application Publication No. 2008/0092309discloses a pretreatment solution for treating textile. The pretreatmentsolution contains a nonionic latex polymer and a multivalent cationicsalt solution. US Patent Application Publication No. 2014/356555discloses an inkjet printing media containing base substrate and acoating layer. The coating layer contains a source of polyvalent ionsand a latex binder that forms a coherent film in the presence of thepolyvalent ions. The base substrate may include paper, cloth, nonwovenfabric, felt, and synthetic (non-cellulosic) papers. However, thesedisclosures do not address printing on a non-porous plastic filmsubstrate which differs from other common substrates in that anon-porous plastic film is completely non-liquid permeable and difficultto adhere to due to weak interaction between plastic polymers and inks,and that a non-porous plastic often requires low drying and curingtemperatures because it is less tolerant to heat. Furthermore, clearnon-porous plastic films, which are widely used in packagingapplication, require a special primer that can afford film clarity. Inaddition, different from printing on paper, printing on a clear ortransparent film commonly requires a white ink to be printed on top ofor beneath the colored image to enhance contrast and make the coloredimage more visually distinctive.

A need exists for an improved inkjet ink set and primer fluidcombination that can produce higher quality print images on non-porousplastic film surfaces, especially with better film clarity for clearnon-porous plastic films. The present disclosure satisfies this need byproviding an inkjet ink and primer fluid set containing a primer, andinkjet inks. The primer forms a coating with a limited increase in haze,and interacts with the inkjet inks to achieve higher quality printimages on non-porous plastic films.

SUMMARY OF THE DISCLOSURE

An embodiment of the present disclosure provides an inkjet ink andprimer fluid set comprising:

-   -   a) an aqueous primer composition comprising a multivalent cation        salt and a polymeric binder, wherein said composition forms a        coating with a dry thickness of from 0.4 to 5.0 micron upon        application onto a non-porous plastic substrate, and said        coating results in a haze increase of less than 10 on said        substrate, said multivalent cation salt is present at an amount        less than 20 wt %, based on the total weight of the primer        composition, and said polymeric binder is not soluble in water,        is stable in the presence of said multivalent cation, and is        selected from the group consisting of urethane polymer, acrylic        polymer and vinyl polymer;    -   b) an aqueous white inkjet ink comprising a titanium oxide        pigment dispersion, and a polyurethane binder or an acrylic        binder, wherein said titanium oxide pigment dispersion having a        particle size with D50 in the range of 200 to 350 nm; and    -   c) one or more aqueous non-white colored inkjet inks, wherein at        least one of the inks comprising a pigment dispersion, and a        second polyurethane binder or a second acrylic binder.

Another embodiment provides that the aqueous primer composition furthercomprising silica particles.

Another embodiment provides that the coating results in a haze increaseof less than 5 on said substrate.

Another embodiment provides that the polyurethane binder and the secondpolyurethane binder are the same.

Another embodiment provides that the acrylic binder and the secondacrylic binder are the same.

Another embodiment provides that the polymeric binder is urethanepolymer.

Another embodiment provides that the polymeric binder is acrylicpolymer.

Another embodiment provides a method of digitally printing an image ontoa non-porous plastic substrate comprising the steps of:

-   -   (a) providing an inkjet printer that is responsive to digital        data signals;    -   (b) providing a non-porous plastic substrate;    -   (c) applying an aqueous primer composition comprising a        multivalent cation salt and a polymeric binder onto the        non-porous plastic substrate to form a coating with a dry        thickness of from 0.4 to 5.0 micron, wherein said coating        results in a haze increase of less than 10 on said substrate,        said multivalent cation salt is present at an amount less than        20 wt %, based on the total weight of the primer composition,        and said polymeric binder is not soluble in water, is stable in        the presence of said multivalent cation, and is selected from        the group consisting of urethane polymer, acrylic polymer and        vinyl polymer;    -   (d) loading the printer with an aqueous white inkjet ink and one        or more aqueous non-white colored inkjet inks, wherein said        white inkjet ink comprising a titanium oxide pigment dispersion,        and a polyurethane binder or an acrylic binder, said titanium        oxide pigment dispersion having a particle size of D50 in the        range of 200 to 350 nm; and wherein at least one of the aqueous        non-white colored inkjet inks comprising a pigment dispersion,        and a second polyurethane binder or a second acrylic binder; and    -   (e) printing onto the primer coated substrate of step (c) using        the white inkjet ink and non-white colored inkjet inks in        response to digital signals.

Another embodiment provides that the digital signals cause the whiteinkjet ink to be printed before the non-white colored inkjet inks areprinted in step (e) above.

Yet another embodiment provides that the digital signals cause the whiteinkjet ink to be printed after the non-white colored inkjet inks areprinted in step (e) above.

DETAILED DESCRIPTION

Unless otherwise stated or defined, all technical and scientific termsused herein have commonly understood meanings by one of ordinary skillin the art to which this disclosure pertains.

Unless stated otherwise, all percentages, parts, ratios, etc., are byweight.

When an amount, concentration, or other value or parameter is given aseither a range, preferred range or a list of upper preferable values andlower preferable values, this is to be understood as specificallydisclosing all ranges formed from any pair of any upper range limit orpreferred value and any lower range limit or preferred value, regardlessof whether ranges are separately disclosed. Where a range of numericalvalues is recited herein, unless otherwise stated, the range is intendedto include the endpoints thereof, and all integers and fractions withinthe range.

When the term “about” is used in describing a value or an end-point of arange, the disclosure should be understood to include the specific valueor end-point referred to.

As used herein, the term “dispersion” means a two-phase system whereinone phase consists of finely divided particles (often in a colloidalsize range) distributed throughout a bulk substance, the particles beingthe dispersed or internal phase and the bulk substance being thecontinuous or external phase.

As used herein, the term “dispersant” means a surface active agent addedto a suspending medium to promote uniform and maximum separation ofextremely fine solid particles often of colloidal sizes. For pigments,the dispersants are most often polymeric dispersants, and thedispersants and pigments are usually combined using a dispersingequipment.

As used herein, the term “aqueous vehicle” refers to water or a mixtureof water and at least one water-soluble, or partially water-soluble(i.e., methyl ethyl ketone), organic solvent (co-solvent).

As used herein, the term “substantially” means being of considerabledegree, almost all.

As used herein, the term “dyne/cm” means dyne per centimetre, a surfacetension unit.

As used herein, the term “cP” means centipoise, a viscosity unit.

The materials, methods, and examples herein are illustrative only exceptas explicitly stated, and are not intended to be limiting.

In addition, references in the singular may also include the plural (forexample, “a” and “an” may refer to one, or one or more) unless thecontext specifically states otherwise.

Non-Porous Plastic Substrate

Non-porous plastic substrate or film is one of the main substrates usedin flexible packaging. Flexible packaging is a container made ofmaterials that can be quickly changed in shape when they're filled orclosed. These containers can use paper, non-porous plastic film or foilmaterials in any combination. A non-porous plastic film typicallyincludes, but not limited to, the following:

High Density Polyethylene (HDPE),

Low Density Polyethylene (LDPE) Includes Linear Low Density Polyethylene(LLDPE),

Polyethylene Terephthalate (PET), Metallized PET (Met-PET), glass coatedPET, acrylic coated PET,

Polypropylene (PP) includes Casted PP (CPP), Oriented PP (OPP), BiaxialOriented PP (BOPP) and Metallized OPP (MOPP),

Polystyrene,

Nylon,

Polyvinyl Chloride (PVC, Vinyl),

Ethylene Vinyl Acetate polymer (EVA), and

Ethylene Vinyl Alcohol copolymer (EVOH).

Each film features different capabilities and characteristics that makesit suitable for specific applications. Alternatively, the films can becombined to create multilayer films with distinct barrier properties forbetter protection or longer shelf life. The customization elementextends to visual properties as well, including clarity, glossiness, andhigh-quality printed graphics in an array of colors and designs to wrapthe product in style and to include important information right on thepackage. These substrate films may be non-oriented or oriented films.The thickness of the substrate film is not critical, but usually onlyneeds to be in the range of 1 to 500 μm. The print surface of thesubstrate film has preferably been treated with a corona discharge.Silica or alumina, for example, may have been deposited on the surfaceof the film.

Primer Composition

The aqueous primer fluid should comprise sufficient ink-aggregatingagent to provide adequate fixation of the inkjet inks. Typically, theprimer will comprise at least about 0.5 wt % of the ink-aggregatingagent, and amounts can be used up to the solubility limits of theparticularly ink-aggregating agent utilized. Preferably, the primer willcomprise from about 1 wt % to about 30 wt % of the ink-aggregatingagent, based on the total weight of the primer fluid.

A polymeric binder is combined with an ink-aggregating agent to form aprimer fluid. The polymeric binder is advantageously used at levels,based on the total weight of ink, of at least about 5%, and typically atleast about 10%. Upper limits are dictated by primer viscosity or otherphysical limitations. In a more typical embodiment, no more than about50% polymeric binder is present in the primer composition, and even mosttypically no more than about 40%, based on the total weight of theprimer fluid. The combined total weight of the polymeric binder andink-aggregating agent can be up to about 45 wt %, based on the totalweight of the primer fluid.

The Primer composition further comprises a surfactant to provide wettingon film substrate. Some suitable surfactants include surfactants thatare miscible with ink-aggregating agent and polymers, i.e., those thatdo not form precipitates or aggregates when mixing. Some usefulsurfactants include cationic, non-ionic, and amphoteric surfactants.Some suitable cationic surfactants include, for example, quaternizedammonium or pyridinium surfactants, such as dodecyltrimethylammoniumchloride, cetyltrimethylammonium bromide, cetyltrimethylpyridiniumchloride and others. Some suitable non-ionic surfactants includeethoxylated acetylene diols (e.g. Surfynol® series from Evonik),ethoxylated primary alcohols (e.g. Neodol® series from Shell) andsecondary alcohols (e.g. Tergitol® series from Dow Chemical), Pluronic®block copolymer surfactants, sulfosuccinates (e.g. Aerosol® series fromCytec), organosilicones (e.g. Dynol™ series from Evonik) and fluorosurfactants (e.g. Zonyl® series from Chemours). Amphoteric surfactantsthat, within a certain pH range, are cationic may also be used. In thiscase the pH of the liquid composition must be adjusted below theisoelectric point of the surfactant. Some examples of usefulzwitterionic surfactants include N,N-dimethyl-N-tetradecyl amine oxide(NTAO), N,N-dimethyl N-hexadecyl amine oxide (NHAO) and related amineoxide compounds. Another example is N-dodecyl-N,N-dimethyl glycine. Yetother examples include phosphates, phosphites, phosphonates, lecithinsand the like, and phosphonate esters such as phosphomyelin. Surfactantsmay be used, typically in the amount of about 0.1 to about 10% and moretypically about 0.5 to about 5%, based on the total weight of the primerfluid.

Primer may further comprise additional additives to modify viscosity,prevent film curling or improve block resistance including, but notlimit to, colloidal silica dispersion and wax emulsion. Preferredcolloidal silica dispersions are nano-size silica particles stabilizedby cationic charge, or no charge as long as the silica dispersions arestable when mixing with ink aggregating agent. Examples include surfacetreated silica SNOWTEX® ST-AK, ST-AK-ML, ST-AK-L, ST-AK-A and ST-AK-XK(Nissan Chemical America, Houston Tex.), and silica with elongated shapeSNOWTEX® ST-OUP and string-of-pearls SNOWTEX® ST-PS-SO and ST-PS-MO.Colloidal silica may be used typically in the amount of 1% to 50% basedon the total weight of the primer fluid. Examples of wax emulsionsinclude, but not limit to, olefin wax such as LDPE, HDPE and PP,paraffin wax, carnauba wax, and amide wax colloidal stabilized withnon-ionic emulsification so it is stable when mix with ink aggregatingagent. Preferred wax examples are AQUACER 539, AQUACER 513, AQUACER 519and AQUACER 497 (BYK-Chemie Wesel, Germany). Wax may be used, typicallyin the amount of 0.05% to 5%, based on the total weight of the primerfluid, as long as the primer coating is transparent.

Other ingredients in the primer solution may further include, but arenot limited to, humectants and biocides. Biocides prevent microbialdegradation—their selection and use is generally well known in the art.Suitable humectants are the same as those suitable for use in coloredinkjet inks, as discussed in further detail below.

Ink-Aggregating Agent

The primer solution contains an ink-aggregating agent that“precipitates” or “crashes” with a colorant or other ingredient(s) in anink. Preferred ink-aggregating agents include multivalent metal salts,and/or organic acid.

“Multivalent” indicates an oxidation state of two or more and, for anelement “Z”, are typically described as Z²⁺, Z³⁺, Z⁴⁺ and so forth. Forbrevity, multivalent cations may be referred to herein as Z^(x). Themultivalent cations are substantially soluble in the aqueous primersolution and preferably exist (in solution) in a substantially ionizedstate so that they are in a form where they are free and available tointeract with the inkjet inks.

Z^(x) includes, but is not limited to multivalent cations of thefollowing elements: Mg, Ca, Sr, Ba, Sc, Y, La, Ti, Zr, V, Cr, Mn, Fe,Ru, Co, Rh, Ni, Pd, Pt, Cu, Au, Zn, Al, Ga, In, Sb, Bi, Ge, Sn, Pb. Inanother embodiment, the multivalent cation comprises at least one of Mg,Ca, Ba, Ru, Co, Zn and Ga. In yet another embodiment, the multivalentcation comprises at least one of Ca, Ba, Ru, Co, Zn and Ga. Preferablythe multivalent cations are Mg and Ca.

Z^(x) can be incorporated into primer solution by addition in a saltform or by addition in an alkaline form and used as a base in theadjustment of the primer solution pH.

The associated anionic material can be chosen from any common anionicmaterial, especially halides, nitrates and sulfates. The anionic form ischosen so that the multivalent cation is soluble in the aqueous primersolution. The multivalent cationic salts can be used in their hydratedform. One or more multivalent cationic salts may be used in the primersolution.

For Ca, the preferred multivalent cation salts are calcium chloride,calcium nitrate, calcium nitrate hydrate and mixtures thereof.

For Mg, the preferred multivalent cation salts are magnesium chloride,magnesium nitrate, magnesium nitrate hydrate, and mixtures thereof.

An organic acid as aggregating agent precipitates ink drops by loweringthe ink's pH and coagulating pigment dispersion and other inkcomponents. Specific examples of acids are polyacrylic acid, aceticacid, glycolic acid, malonic acid, maleic acid, ascorbic acid, succinicacid, glutaric acid, fumaric acid, citric acid, tartaric acid, lacticacid, sulfonic acid, orthophosphoric acid, pyrrolidone carboxylic acid,pyrone carboxylic acid, pyrrole carboxylic acid, furan carboxylic acid,pyridine carboxylic acid, coumaric acid, thiophene carboxylic acid,nicotinic acid and derivatives of these compounds. Polyacrylic acid andacetic acid are particularly preferred

Primer Polymeric Binder

The primer solution contains compatible polymeric binder(s) which do not“precipitate” or “crash” with the aggregating agent. The primerpolymeric binder and ink-aggregating agent solution thus formed must bestable as a solution or as a stable emulsion to permit the coating ofthe film substrate. If the primer polymeric binder gels, or its emulsionprecipitates in the presence of an ink-aggregating agent, e.g., amultivalent cationic salt solution, then it cannot be used as a primeradditive. A screening test to determine whether a primer polymericbinder is stable in the presence of an ink-aggregating agent is to mix a10 wt % polymer (on a dry basis) and a 15 wt % of calcium nitratetetrahydrate and observe whether the solution/emulsion is stable. Thestability is observed at ambient temperature (˜25° C.), and at intervalsof 10 minutes and 24 hours. The primer polymeric binder must lead to astable polymer/multivalent cationic solution/emulsion mixture.

Some suitable compatible polymeric binders include, for example,non-ionic water insoluble polymers in colloidal particle form whichinclude acrylic latexes, polyurethane dispersions, vinyl acetatecopolymer latexes, polyester and polyamide dispersions. These polymersmay be made by any known process including, but not limited to, freeradical, group transfer, ionic, RAFT, condensation and other types ofpolymerization.

A primer polymeric binder can be formed from the incorporation of anonionic stabilizer either chemically bound or physically absorbed intothe polymer. Examples of nonionic reactive components include, ethyleneoxide derivatives, acrylamide, hydroxyethyl-substituted monomers,vinylpyrrolidone, ethyleneimines, and the like. The incorporation canoccur during the polymerization step, or after the polymerization stepwhich prepares the latex polymer. In the case of an ethylene oxidenonionic component, the substitution can take the form of incorporatinga glycol with sufficient (—CH₂—CH₂O—)_(n) units to impart the nonionicstability. For instance, a polyurethane may have an alkyl polyethyleneglycol incorporated into the nonionic polyurethane. The nonioniccomponent can be the main component in nonionic latex polymer, as longas its properties satisfy the stability test described above.

A primer polymeric binder may also have ionic components incorporatedinto the polymer. By example, for the polyurethanes ionic componentssuch as acids may be used in the polyurethane reaction and a specificacid example is dimethylolpropionic acid. For the acrylamide andhydroxyethyl substituted nonionic latex polymer, the ionic source can befrom (meth)acrylic acids. There are limits to the amount of ioniccomponents in the polymer, since the ionic components may complex withthe ink-aggregating agent that will lead to instability of thepolymer/multivalent cationic solution. The balance of nonionic and ioniccomponents must lead to a stable solution as described above.

Application of Primer

Prior to printing inkjet inks, film substrate is coated with the primerfluid via various coating methods available including flexographic,gravure, rod, spray, roll, curtain and knife coating methods. Preferredmethods are flexographic, gravure and rod coating methods. Theapplication of the primer is in-line or off-line with the inkjet inkprinting process depending on printer design and machine integration.Regardless of coating methods, primer is sufficiently dried beforeprinting inkjet inks. Drying process is not limited to any method,varying from hot air, infrared and near-infrared radiation, as long asthe temperature is not too high to distort the film integrity. Typicaldrying temperature range from 40° C. to 120° C., preferably from 50° C.to 100° C. The coating thickness of the dried primer can vary from 0.3to 10 μm, preferably from 0.5 to 8 μm, more preferably from 0.6 to 5 μm.By adjusting primer's coating thickness, coating's tackiness, dryingspeed, haziness, adhesion, and ink's image quality can be adjusted andoptimized.

A key desirable feature of clear film packaging is film clarity, whichis commonly measured by haze. Haze is the percentage of lighttransmitted through a film that is deflected more than 2.5° from thedirection of the incoming beam. The lower haze value represents higherfilm clarity and thicker film and extra coating usually contribute toincreased haze. Preferably after primer coating, haze change from thebase film substrate is less than 10, more preferably less than 5.

Ink Sets

The term “ink set” refers to all the individual inks or other fluids aninkjet printer is equipped to jet. The white inks used to print theimage after printing the colored inks or the white ink used to printprior to printing the colored inks are considered part of the ink set.This ink set, together with the primer fluid, forms an inkjet ink andprimer fluid set.

In one preferred embodiment, the ink set comprises at least twodifferently colored inkjet inks, at least one of which is a whitepigmented inkjet ink as described above.

In another preferred embodiment, the ink set comprises at least fourdifferently colored inkjet inks, wherein at least one is a cyan inkjetink, at least one is a magenta inkjet ink, at least one is a yellowinkjet ink, and at least one is a white inkjet ink.

In addition to the colored inkjet inks just mentioned, it is alsopreferable to include a black inkjet ink in the ink set.

In addition to the CMYKW inks mentioned above, the ink sets may containadditional differently colored inks, as well as different strengthversions of the CMYKW and other inks.

For example, the ink sets of the present invention can comprisefull-strength versions of one or more of the inks in the ink set, aswell as “light” versions thereof.

Additional colors for the inkjet ink set include, for example, orange,violet, green, red and/or blue.

The preferred inks in the ink sets are pigmented inks.

Pigments

The colorant used for printing the colored image may be a dye or apigment. Dyes include disperse dyes, reactive dyes, acid dyes and thelike. The term “pigment” as used herein means an insoluble colorant thatrequires to be dispersed with a dispersant and processed underdispersive conditions in the presence of a dispersant. Pigmented inksare preferred.

Pigments suitable for being used are those generally well-known in theart for aqueous inkjet inks. The selected pigment(s) may be used in dryor wet form. For example, pigments are usually manufactured in aqueousmedia, and the resulting pigments are obtained as a water-wet presscake.In presscake form, the pigment does not agglomerate to the extent itwould in dry form. Thus, pigments in water-wet presscake form do notrequire as much mixing energy to de-agglomerate in the premix process aspigments in dry form. Representative commercial dry pigments are listedin U.S. Pat. No. 5,085,698.

Some examples of pigments with coloristic properties useful in inkjetinks include, but not limited to: cyan pigments from Pigment Blue 15:3and Pigment Blue 15:4; magenta pigments from Pigment Red 122 and PigmentRed 202; yellow pigments from Pigment Yellow 14, Pigment Yellow 74,Pigment Yellow 95, Pigment Yellow 110, Pigment Yellow 114, PigmentYellow 128 and Pigment Yellow 155; red pigments from Pigment Orange 5,Pigment Orange 34, Pigment Orange 43, Pigment Orange 62, Pigment Red 17,Pigment Red 49:2, Pigment Red 112, Pigment Red 149, Pigment Red 177,Pigment Red 178, Pigment Red 188, Pigment Red 254, Pigment Red 184,Pigment Red 264 and Pigment Red PV19; green pigments from Pigment Green1, Pigment Green 2, Pigment Green 7 and Pigment Green 36; blue pigmentsfrom Pigment Blue 60, Pigment Violet 3, Pigment Violet 19, PigmentViolet 23, Pigment Violet 32, Pigment Violet 36 and Pigment Violet 38;and black pigment carbon black. The pigment names and abbreviations usedherein are the “C.I.” designation for pigments established by Society ofDyers and Colourists, Bradford, Yorkshire, UK and published in The ColorIndex, Third Edition, 1971.

Examples of white color materials include, but are not limited to, whiteinorganic pigments such as Titanium Oxide, Zinc Oxide, zinc sulfide,antimony oxide, and zirconium oxide. Besides such white inorganicpigments, white organic pigments such as white hollow resin particlesand polymeric particles can also be used. The preferred pigment for theaqueous pigmented white ink is titanium dioxide. Titanium dioxide (TiO2)pigment useful may be in the rutile or anatase crystalline form. It iscommonly made by either a chloride process or a sulfate process. In thechloride process, TiCl4 is oxidized to TiO2 particles. In the sulfateprocess, sulfuric acid and ore containing titanium are dissolved, andthe resulting solution goes through a series of steps to yield TiO2.Both the sulfate and chloride processes are described in greater detailin “The Pigment Handbook”, Vol. 1, 2nd Ed., John Wiley & Sons, NY(1988), the relevant disclosure of which is incorporated by referenceherein for all purposes as if fully set forth.

The titanium dioxide particles can have a wide variety of averageparticle sizes of about 1 micron or less, depending on the desired enduse application of the ink. For applications demanding high hiding ordecorative printing applications, the titanium dioxide particlespreferably have an average size of less than about 1 micron (1000nanometers). Preferably, the particles have an average size of fromabout 50 to about 950 nanometers, more preferably from about 75 to about750 nanometers, and still more preferably from about 100 to about 500nanometers. These titanium dioxide particles are commonly calledpigmentary TiO2.

For applications demanding white color with some degree of transparency,the pigment preference is “nano” titanium dioxide. “Nano” titaniumdioxide particles typically have an average size ranging from about 10to about 200 nanometers, preferably from about 20 to about 150nanometers, and more preferably from about 35 to about 75 nanometers. Anink comprising nano titanium dioxide can provide improved chroma andtransparency, while still retaining good resistance to light fade andappropriate hue angle. A commercially available example of an uncoatednano grade of titanium oxide is P-25, available from Evonik (ParsippanyN.J.).

The titanium dioxide pigment may be substantially pure titanium dioxideor may contain other metal oxides, such as silica, alumina and zirconia.Other metal oxides may become incorporated into the pigment particles,for example, by co-oxidizing or co-precipitating titanium compounds withother metal compounds. If co-oxidized or co-precipitated metals arepresent, they are preferably present as the metal oxide in an amountfrom about 0.1 wt % to about 20 wt %, more preferably from about 0.5 wt% to about 5 wt %, and still more preferably from about 0.5 wt % toabout 1.5 wt %, based on the total titanium dioxide pigment weight.

The titanium dioxide pigment may also bear one or more metal oxidesurface coatings. These coatings may be applied using techniques knownby those skilled in the art. Examples of metal oxide coatings includesilica, alumina, alumina-silica, boria and zirconia, among others. Suchcoatings may optionally be present in an amount of from about 0.1 wt %to about 10 wt %, and preferably from about 0.5 wt % to about 3 wt %,based on the total weight of the titanium dioxide pigment. Thesecoatings can provide improved properties including reducing thephotoreactivity of the titanium dioxide. Commercial examples of suchcoated titanium dioxides include R700 (alumina-coated, available fromChemours, Wilmington Del.), RDI-S (alumina-coated, available from KemiraIndustrial Chemicals, Helsinki, Finland), R706 (available from Chemours,Wilmington Del.) and W-6042 (a silica alumina treated nano gradetitanium dioxide from Tayco Corporation, Osaka Japan).

The titanium dioxide pigment may also bear one or more organic surfacecoatings, such as, for example, carboxylic acids, silanes, siloxanes andhydrocarbon waxes, and their reaction products with the titanium dioxidesurface. The amount of organic surface coating, when present, generallyranges from about 0.01 wt % to about 6 wt %, preferably from about 0.1wt % to about 3 wt %, more preferably about 0.5 wt % to about 1.5 wt %,and still more preferably about 1 wt %, based on the total weight of thepigment.

Polymeric Dispersant

Traditionally, pigments are stabilized by dispersing agents, such aspolymeric dispersants or surfactants, to produce a stable dispersion ofthe pigment in the vehicle. More recently though, so-called“self-dispersible” or “self-dispersing” pigments (hereafter “SDP”) havebeen developed. As the name would imply, SDPs are dispersible in waterwithout dispersants. Dispersed dyes are also considered pigments as theyare insoluble in the aqueous inks used herein.

The polymeric dispersant for the non-self-dispersing pigment(s) may be arandom or a structured polymer. Typically, the acrylic based polymerdispersant is a copolymer of hydrophobic and hydrophilic monomers. Someexamples of hydrophobic monomers used are methyl methacrylate, n-butylmethacrylate, 2-ethylhexyl methacrylate, benzyl methacrylate,2-phenylethyl methacrylate and the corresponding acrylates. Examples ofhydrophilic monomers are methacrylic acid, acrylic acid,dimethylaminoethyl(meth)acrylate and salts thereof. Quaternary salts ofdimethylaminoethyl(meth)acrylate may also be employed. The “randompolymer” means polymers where molecules of each monomer are randomlyarranged in the polymer backbone. For a reference on suitable randompolymeric dispersants, see: U.S. Pat. No. 4,597,794. The “structuredpolymer” means polymers having a block, branched, graft or starstructure. Examples of structured polymers include AB or BAB blockcopolymers such as the ones disclosed in U.S. Pat. No. 5,085,698; ABCblock copolymers such as the ones disclosed in EP Patent SpecificationNo. 0556649; and graft polymers such as the ones disclosed in U.S. Pat.No. 5,231,131. Other polymeric dispersants that can be used aredescribed, for example, in U.S. Pat. Nos. 6,117,921, 6,262,152,6,306,994 and 6,433,117.

The “random polymer” also includes polyurethanes. Particularly usefulare the polyurethane dispersant disclosed in U.S. Patent ApplicationPublication No. 2012/0214939 where the polyurethane dispersant iscrosslinked after dispersing a pigment to form a pigment dispersion.

Colored Pigment Dispersion

The color pigment dispersion which are stabilized by added polymerdispersant may be prepared by methods known in the art. It is generallydesirable to make the stabilized pigment in a concentrated form. Thestabilized pigment is first prepared by premixing the selectedpigment(s) and polymeric dispersant(s) in an aqueous carrier medium(such as water and, optionally, a water-miscible solvent), and thendispersing or deflocculating the pigment. The premixing step isgenerally done in a stirred mixing vessel, and a high-speed disperser(HSD) is particularly suitable for the mixing step. A Cowels type bladeattached to the HSD and operated at from 500 rpm to 4000 rpm, and moretypically from 2000 rpm to 3500 rpm, provides optimal shear to achievethe desired mixing. Adequate mixing is usually achieved after mixingunder the conditions described above for a period of from 15 to 120minutes. The subsequent dispersing step may be accomplished in a 2-rollmill, media mill, a horizontal mini mill, a ball mill, an attritor, orby passing the mixture through a plurality of nozzles within a liquidjet interaction chamber at a liquid pressure of at least 5,000 psi toproduce a uniform dispersion of the pigment particles in the aqueouscarrier medium (microfluidizer). Alternatively, the concentrates may beprepared by dry milling the polymeric dispersant and the pigment underpressure. The media for the media mill is chosen from commonly availablemedia, including zirconia, YTZ and nylon. These various dispersionprocesses are in a general sense well known in the art, as exemplifiedby U.S. Pat. Nos. 5,022,592, 5,026,427, 5,310,778, 5,891,231, 5,976,232and US20030089277. The disclosures of each of these publications areincorporated by reference herein for all purposes as if fully set forth.Preferred are 2-roll mill, media mill, and by passing the mixturethrough a plurality of nozzles within a liquid jet interaction chamberat a liquid pressure of at least 5,000 psi.

After the milling process is complete the color pigment concentrate maybe “let down” into an aqueous system. “Let down” refers to the dilutionof the concentrate with mixing or dispersing, the intensity of themixing/dispersing normally being determined by trial and error usingroutine methodology, and often being dependent on the combination of thepolymeric dispersant, solvent and pigment.

The range of useful particle size after dispersion is typically fromabout 0.005 micrometers to about 15 micrometers. Typically, the pigmentparticle size should range from about 0.005 micrometers to about 5micrometers; and, specifically, from about 0.005 micrometers to about 1micrometers. The average particle size as measured by dynamic lightscattering is less than about 500 nm, typically less than about 300 nm.

White Pigment Dispersion

One or more dispersants described for colored pigment are also employedto stabilize the titanium dioxide. It is generally desirable to make thestabilized TiO2 pigment in concentrated slurry form. TiO2 slurry isgenerally done in a stirred mixing vessel, and a high-speed disperser(HSD) is particularly suitable for the mixing step. A Cowels type bladeattached to the HSD and operated at from 500 rpm to 4000 rpm, and moretypically from 2000 rpm to 3500 rpm, provides optimal shear to achievethe desired mixing. Adequate mixing is usually achieved after mixingunder the conditions described above for a period of from 15 to 600minutes. The amount of titanium dioxide present in the slurrycomposition is preferably from about 35 wt % to about 80 wt %, based onthe total slurry weight, more preferably from about 50 wt % to about 75wt %, based on the total weight of the slurry. The titanium dioxide hasa 50% average particle size (hereinafter referred to as “D50”) that ispreferably in the range of 50 to 500 nm, more preferably in the range of150 to 350 nm. The titanium dioxide having a D50 within these rangesenables printed film to exhibit satisfactory opacity of the image, whichenables formation of an image with high quality.

In the case of color pigments, the ink may contain up to approximately30%, preferably about 0.1 to about 25%, and more preferably about 0.25to about 10%, pigment by weight based on the total ink weight. If aninorganic pigment such as TiO2 pigment is selected, the ink will tend tocontain higher weight percentages of pigment than with comparable inksemploying color pigment, and may be as high as about 75% in some cases,since inorganic pigments generally have higher specific gravities thanorganic pigments.

Post Modification of a Polymeric Dispersant After Formation of a PigmentDispersion

The polymeric dispersant dispersing a pigment may be crosslinked after apigment dispersion is prepared to form a crosslinked pigment dispersionprior to its inclusion in an inkjet ink. The crosslinkable polymericdispersant are polymers substituted with crosslinkable moieties selectedfrom the group consisting of acetoacetoxy, acid, amine, epoxy, hydroxyl,blocked isocyanates and mixtures thereof. The crosslinking agent isselected from a group consisting of acetoacetoxy, acid, amine,anhydride, epoxy, hydroxyl, isocyanates, blocked isocyanates andmixtures thereof. In the crosslinking step, a crosslinking agent isadded to the pigment dispersion after the pigment is dispersed andcrosslinking took place by heating the mixture for several hours atelevated temperature. After the crosslinking step excess polymer can beremoved by purification processes such as ultrafiltration. Specificexamples of crosslinking moiety/agent pairs are hydroxyl/isocyanate andacid/epoxy.

Ink Polymeric Binder

An ink binder for CMYKW inks is a polymeric compound or a mixture ofpolymeric compounds that is added to an ink formulation. The binder canimpart properties to the printed material that, for example, givesgreater durability to the printed material. Typical polymers used asbinders in inkjet inks include polyurethane dispersions and polyurethanesolutions, acrylics, styrene acrylics, styrene butadienes, styrenebutadiene acrylonitriles, neoprenes, ethylene acrylic acids, ethylenevinyl acetate emulsions, latexes and the like. The binder may be asolution or stabilized as an emulsion by having ionic substituents suchas carboxylic acids, sulfur containing acids, amine groups, and othersimilar ionic groups. Alternatively, the binder may be stabilized byexternal surfactants. The binder can be used singly or in combinationwith other binders. Typically, the binder is a polyurethane and acrylic.The binder is typically present in an ink in an amount of at least 0.2%by weight based on the total weight of the ink. Examples of ink binderpolymer include polyurethane polymers such as Takelac® WS5100, Takelac®WS4022, Takelac® W5030, XW-Um601 and XW-Um602A from Mitsui Chemicals(Tokyo, Japan); Acrylic polymers such as Johncryl® FLX5000-A, Johncryl®FLX5220 and Johncryl® FLX5026A from BASF (Ludwigshafen, Germany).

Typically, a binder is different from the polymer dispersant describedabove and is neither reactive nor adsorptive to the colorant. The binderis typically added to an ink during the final formulation stage, notduring the preparation of a pigment dispersion. The binder is typicallypresent in an ink in an amount of at least 0.2% by weight, based on thetotal weight of the ink. The amount can be from 1 to 15 wt %, based onthe total weight of the ink.

Ink Vehicle

The pigmented ink of this disclosure comprises an ink vehicle typicallyan aqueous ink vehicle, also known as an aqueous carrier medium, theaqueous dispersion and optionally other ingredients.

The ink vehicle is the liquid carrier (or medium) for the aqueousdispersion(s) and optional additives. The term “aqueous ink vehicle”refers to an ink vehicle comprised of water or a mixture of water andone or more organic, water-soluble vehicle components commonly referredto as co-solvents or humectants. Selection of a suitable mixture dependson requirements of the specific application, such as desired surfacetension and viscosity, the selected pigment, drying time of thepigmented ink jet ink, and the type of media onto which the ink will beprinted.

Examples of water-soluble organic solvents and humectants include:alcohols, ketones, keto-alcohols, ethers and others, such asthiodiglycol, Sulfolane, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinoneand caprolactam; glycols such as ethylene glycol, diethylene glycol,triethylene glycol, tetraethylene glycol, propylene glycol, dipropyleneglycol, tripropylene glycol, trimethylene glycol, butylene glycol andhexylene glycol; addition polymers of oxyethylene or oxypropylene suchas polyethylene glycol, polypropylene glycol and the like; triols suchas glycerol and 1,2,6-hexanetriol; lower alkyl ethers of polyhydricalcohols, such as ethylene glycol monomethyl ether, ethylene glycolmonoethyl ether, diethylene glycol monomethyl, diethylene glycolmonoethyl ether; lower dialkyl ethers of polyhydric alcohols, such asdiethylene glycol dimethyl or diethyl ether; urea and substituted ureas.

A mixture of water and a polyhydric alcohol, such as diethylene glycol,is typical as the aqueous ink vehicle. In the case of a mixture of waterand diethylene glycol, the ink vehicle usually contains from 30% waterand 70% diethylene glycol to 95% water and 5% diethylene glycol, moretypically from 60% water and 40% diethylene glycol to 95% water and 5%diethylene glycol. Percentages are based on the total weight of the inkvehicle. A mixture of water and butyl carbitol is also an effective inkvehicle.

The amount of ink vehicle in the ink is typically in the range of from70% to 99.8%, and more typically from 80% to 99.8%, by weight based ontotal weight of the ink.

The ink vehicle can be made to be rapid drying by including solventssuch as glycol ethers and 1,2-alkanediols. Glycol ethers includeethylene glycol monobutyl ether, diethylene glycol mono-n-propyl ether,ethylene glycol mono-iso-propyl ether, diethylene glycol mono-iso-propylether, ethylene glycol mono-n-butyl ether, ethylene glycol mono-t-butylether, diethylene glycol mono-n-butyl ether, triethylene glycolmono-n-butyl ether, diethylene glycol mono-t-butyl ether,1-methyl-1-methoxybutanol, propylene glycol mono-t-butyl ether,propylene glycol mono-n-propyl ether, propylene glycol mono-iso-propylether, propylene glycol mono-n-butyl ether, dipropylene glycolmono-n-butyl ether, dipropylene glycol mono-n-propyl ether, anddipropylene glycol mono-isopropyl ether. Typical 1,2-alkanediols areC4-C6 alkanediols with 1,2-hexanediol being most typical. The amount ofglycol ether(s) and 1,2-alkanediol(s) added is typically in the range offrom 1% to 15%, and more typically from 2% to 10% by weight, based onthe total weight of the ink.

Surfactants are commonly added to inks to adjust surface tension andwetting properties. Suitable surfactants include ethoxylated acetylenediols (e.g. Surfynol® series commercially available from Evonik),ethoxylated alkyl primary alcohols (e.g. Neodol® series commerciallyavailable from Shell) and secondary alcohols (e.g. Tergitol® seriescommercially available from Dow Chemical), sulfosuccinates (e.g.Aerosol® series commercially available from Cytec), organosilicones(e.g. DYNOL™ series commercially available from Evonik) and fluorosurfactants (e.g. CAPSTONE™ series commercially available fromChemours). Surfactants are typically used in amounts up to about 3% andmore typically in amounts up to 1% by weight, based on the total weightof the ink.

Other ingredients, additives, may be formulated into the inkjet ink, tothe extent that such other ingredients do not interfere with thestability and jettability of the inkjet ink. This may be readilydetermined by routine experimentation by one skilled in the art.

Inclusion of sequestering (or chelating) agents such asethylenediaminetetraacetic acid, iminodiacetic acid,ethylenediamine-di(o-hydroxyphenylacetic acid), nitrilotriacetic acid,dihydroxyethylglycine, trans-1,2-cyclohexanediaminetetraacetic acid,diethylenetriamine-N,N,N′,N″,N″-pentaacetic acid, andglycoletherdiamine-N,N,N′,N′-tetraacetic acid, and salts thereof, may beadvantageous, for example, to eliminate deleterious effects of heavymetal impurities.

Biocides may be used to inhibit growth of microorganisms.

Ink Properties

Jet velocity, separation length of the droplets, drop size and streamstability are greatly affected by the surface tension and the viscosityof the ink. Pigmented ink jet inks typically have a surface tension inthe range of about 20 dyne/cm to about 45 dyne/cm at 25° C. Viscositycan be as high as 30 cP at 25° C., but is typically much lower, moretypically less than 10 cP at 25° C. The ink has physical propertiescompatible with a wide range of ejecting conditions, i.e., drivingfrequency of the piezo element or ejection conditions for a thermal headfor either a drop-on-demand device or a continuous device, and the shapeand size of the nozzle. The inks should have excellent storage stabilityfor long periods so as not to clog to a significant extent in an ink jetapparatus. Furthermore, the ink should not corrode parts of the ink jetprinting device it comes in contact with, and it should be essentiallyodorless and non-toxic. Preferred pH for the ink is in the range of fromabout 6.5 to about 8.5.

Printing

The present method relates to digitally printing a non-porous plasticfilm substrate. Typically, this involves the following steps:

-   -   (a) providing an inkjet printer that is responsive to digital        data signals;    -   (b) providing a non-porous plastic substrate;    -   (c) applying an aqueous primer composition comprising a        multivalent cation salt and a polymeric binder onto the        non-porous plastic substrate to form a coating with a dry        thickness of from 0.4 to 5.0 micron, wherein said coating        results in a haze increase of less than 10 on said substrate,        said multivalent cation salt is present at an amount less than        20 wt %, based on the total weight of the primer composition,        and said polymeric binder is not soluble in water, is stable in        the presence of said multivalent cation, and is selected from        the group consisting of urethane polymer, acrylic polymer and        vinyl polymer;    -   (d) loading the printer with an aqueous white inkjet ink and one        or more aqueous non-white colored inkjet inks, wherein said        white inkjet ink comprising a titanium oxide pigment dispersion,        and a polyurethane binder or an acrylic binder, said titanium        oxide pigment dispersion having a particle size of D50 in the        range of 200 to 350 nm; and wherein at least one of the aqueous        non-white colored inkjet inks comprising a pigment dispersion,        and a second-polyurethane binder or a second acrylic binder; and    -   (e) printing onto the primer coated substrate of step (c) using        the white inkjet ink and non-white colored inkjet inks in        response to digital signals.

In step (e), the white ink can be printed first as a background imagefollowed by color ink. Alternatively, the non-white colored inks can befirst printed and then covered by the white ink in a reverse printingsetting. Drying between the non-white colored inks or between white andnon-white colored inks are optional.

Printing can be accomplished by any inkjet printer equipped for handlingand printing film substrate. Film printed with pigmented inks will bedried at elevated temperature after printing. Temperature range variedwith printer and dryer design and line speed, as long as it is not toohigh to cause damage on the films. Generally, drying temperatures willbe at highest 120° C. and preferably not higher than 100° C., morepreferably not above 95° C.

Examples

The invention is further illustrated by, but not limited to, thefollowing examples, in which parts and percentages are by weight unlessotherwise noted.

Ingredients and Abbreviations

DBTL=dibutyltindilaurate

DMPA=dimethylol propionic acid

EDA=ethylene diamine

IPDI=isophoronediisocyanate

TEA=triethylamine

TETA=triethylenetetramine

DETA=diethylenetriamine

MEK=methyl ethyl ketone

TMP=TrimethylolPropane

DMEA=dimethyl ethanolamine

CHDM=1, 4-cyclohexanedimethanol

Unless otherwise noted, the above chemicals were obtained from Aldrich(Milwaukee, Wis.) or other similar suppliers of laboratory chemicals.

Terathane® T650—polyether polyol from Invista (Wilmington, Del.)

Desmorphen® C1200—polyester polyol from Covestro (Leverkusen, Germany)

Tegomer® D3403—polyether polyol from Evonik (Essen, Germany)

Eternacoll®UC-100 and UH-50—polycarbonate polyol from UBE industries(Tokyo, Japan)

Surfynol®440, 420 and 465—nonionic surfactant from Evonik (Essen,Germany) Byk® 348—silicone surfactant from BYK (Wesel, Germany)

Dynol™ 980—silicone surfactant from Evonik (Essen, Germany)

SNOWTEX® ST-AK-ML—nano-silica dispersion from Nissan Chemical America(Houston Tex.)

Aquacer® 513—wax emulsion from BYK (Wesel, Germany)

Takelac™ W6355—waterborne polyurethane resin from Mitsui Chemicals(Tokyo, Japan)

Baybond PU1810/1, Impranil®DLU—waterborne polyurethane resin fromCovestro (Leverkusen, Germany)

Mowinyl 6950—acrylic emulsion resin from Japan Coating Resin Corp.(Osaka, Japan)

Mowinyl 3500—Vinyl acetate copolymer resin from Japan Coating ResinCorp. (Osaka, Japan)

Preparation of Primer Binder Primer Binder P-1

To a dry, alkali- and acid-free flask, equipped with an addition funnel,a condenser, stirrer and a nitrogen gas line were added 55 g CHDM, 130 gTerathane T650, 75 g Tegomer D3403, 10 g DMPA, 7.5 g TEA and 235 g MEK.The contents were heated to 50° C. and thoroughly mixed. 195 g IPDI wasthen added to the flask via the addition funnel at 40° C. over a periodof 5 min, with any residual IPDI being rinsed from the addition funnelinto the flask with 10 g MEK.

The flask temperature was raised to 65° C., held until the NCO % reached2.0% or less. The flask was allowed to cool to 55° C., and 877 gdeionized (DI) water was added over 10 minutes, followed by 73 g DETA(as a 10% solution in water) over 5 minutes, via the addition funnel.The mixture was held at 50° C. for 1 hour, then cooled to roomtemperature.

MEK (˜245 g) was removed under vacuum, leaving a final dispersion ofpolyurethane with about 30.0% of solids by weight.

Following procedures similar to the preparation of Primer Binder P-1,Primer Binders P2-P5 were prepared using ingredients listed in Table 1below.

TABLE 1 Ingredient/ Primer Primer Primer Primer Primer Weight (g) BinderP-1 Binder P-2 Binder P-3 Binder P-4 Binder P-5 IPDI 195 400 462 205 167DMPA 10 19 22 10 10 Terathane 130 200 264 185 T650 Tegomer 75 142 166 9575 D3403 Eternacoll 100 UH50 1,3 30 propanediol TEA 7.5 12.8 14.8 7.57.5 TETA 8.0 TMP 15.4 DETA 7.3 30 30 6 CHDM 55 130 120 28

Additional primer binders used included Takelac W6355, a polyurethanefrom Mitsui Chemical, Baybond PU1810/1, a polyurethane polymer fromCovestro, Mowinyl 6950, an acrylic polymer, and Mowinyl 3500, a vinylacetate polymer from Japan Coating Resin Corporation.

Primers A-N were prepared using ingredients listed in Tables 2 and 3below by combining the listed ingredients with agitation and mixinguntil a homogeneous mixture is obtained.

TABLE 2 Component weight % (dry weight basis) Primer A Primer B Primer CPrimer D Primer E Primer F Calcium nitrate 3.5 tetrahydrate Calciumchloride 0.6 1.5 dihydrate Magnesium Sulfate 1.5 Magnesium Nitrate 3 3hexahydrate 1.2 Propanediol 2.5 1,3 Propanediol 5 2.5 2.5 Surfynol 4650.5 1 1 1 Takelac W6355 35 Primer Binder P-1 33 Primer Binder P-2 33 3333 Primer Binder P-4 27 Snowtex ST-AK-ML 1.6 DI water Balance to 100%

TABLE 3 Component weight % (dry weight basis) Primer G Primer H Primer IPrimer J Primer K Primer L Primer M Primer N Calcium nitratetetrahydrate Calcium chloride 0.9 0.9 dihydrate Magnesium nitrate 3 31.8 1.8 1.8 2.25 hexahydrate 1,3 Propanediol 3 5 5 5 Dipropylene glycol5 methyl ether Surfynol 465 0.5 1 0.5 0.5 0.5 Primer Binder P-1 33Primer Binder P-3 35 Primer Binder P-5 33 6.5 6.5 Baybond 30 PU1810/1Mowinyl 6950 45 Mowinyl 3500 40 Snowtex ST-AK-ML 19 19 Aquacer 513 0.1DI water Balance to 100%

Comparative Primers A and B were prepared using ingredients listed inTable 4 below.

TABLE 4 Component weight % (dry Comparative Comparative weight basis)Primer A Primer B Magnesium Nitrate 2.5 23 hexahydrate 1,3 Propanediol 5Surfynol 465 0.5 Impranil DLU 30 Primer Binder P-5 16 Snowtex ST-AK-ML 7DI Water Balance to 100%

Another comparative primer, Comparative Primer C, PP-17, was supplied byMeisei Chemical Works, LTD. Koyto, Japan.

Mylar MLBT, a clear PET film from DuPont Teijing Film, was coated withthe primer fluid using a Gardco film applicator rod having a wire sizeof 2.5 (Paul N. Gardner Inc., Florida, USA) to form a coating having adry thickness varying from 0.5 to 2.0 micron depending on solids andviscosity. The coating was dried in a 65° C. convection oven for 3minutes. Two types of films were coated. One was a PET film, Mylar MLBTfrom DuPont Teijing Film. Film haze was measured before and aftercoating using a BYK haze-gard i following the ASTM D 1003 method. Beforethe coating of a primer, the Mylar MLBT film has a haze reading of 4.80.

Each treated film's transparency was rated by a visual inspection, andwas given a rating from 1 to 3, with “1” designating no change from thebase film, “2” designating slightly cloudy, and “3” designating cloudyor forming cracks.

The blocking resistance was tested by folding a printed film face toface to itself immediately after drying. A weight was laid on top of thefolded film such that a pressure of 9 kg/cm² was applied for 12 hours.The weight was then lifted and the folded film was pulled apart.Blocking resistance was rated according to the following protocol, andresults are shown in Table 5 below.

-   -   Rating 1, no coating damage and the film falls apart without any        sound    -   Rating 2, no coating damage and the film falls apart with a        cracking sound    -   Rating 3, slight damage of the coating or coating appears to be        cloudy    -   Rating 4, large damage of the coating, such as a coating becomes        peelable from the base film

TABLE 5 Transparency Haze Blocking Primers Rating Haze Change RatingPrimer-A 1 4.56 −0.24 2 Primer-B 1 4.34 −0.46 3 Primer-C 2 6.82 2.26 3Primer-D 1 4.98 0.42 1 Primer-E 1 4.46 −0.1 1 Primer-F 1 4.67 0.11 1Primer-G 2 6.82 2.26 1 Primer-H 1 4.84 0.28 3 Primer-I 1 4.09 −0.47 4Primer-J 1 4.78 0.22 1 Primer-K 1 4.42 −0.14 1 Primer-L 2 5.15 0.59 2Primer-M 1 5.71 1.15 2 Primer-N 2 5.19 0.63 1 Comparative 2 15.73 11.173 Primer A Comparative 3 59 54.4 1 Primer B Comparative 3 96 91.44 1Primer C

CMYK Inks and White Ink Cyan Pigment Dispersion

A cyan dispersion was prepared according to a procedure disclosed inU.S. Patent Application Publication No. 2012/0214939, the disclosure ofwhich is incorporated by reference herewith for all purposes as if fullyset forth. A cyan TRB2 pigment was employed, and the dispersant wascrosslinked after dispersing the pigment.

Yellow Pigment Dispersion

A yellow dispersion was prepared in a similar fashion as the CyanDispersion with the exception of using yellow pigment PY74.

Magenta Pigment Dispersion

A magenta dispersion was prepared in a similar fashion as the CyanDispersion with the exception of using magenta pigment PR122.

Black Pigment Dispersion

A black dispersion was prepared in a similar fashion as the CyanDispersion with the exception of using carbon black pigment.

TiO2 Pigment dispersion

Preparation of Titanium dioxide dispersion can be found in PatentApplication Publication No. US20070060670, which is incorporated byreference herein as if fully set forth.

Ink Polymer Binder PUD-A1

To a dry, alkali- and acid-free flask, equipped with an addition funnel,a condenser, stirrer and a nitrogen gas line were added 15.8 g CHDM,104.7 g Terathane T650, 4.0 g TMP, and 118 g acetone. The contents wereheated to 40° C. and thoroughly mixed. 120 g IPDI was then added to theflask via the addition funnel at 40° C. over 5 min, with any residualIPDI being rinsed from the addition funnel into the flask with 2 gacetone.

The flask temperature was raised to 50° C. After holding at 50° C. for240 minutes, an additional 15.8 g of DMPA, followed by 11 g of TEA, wereadded to the flask via the addition funnel, which was then rinsed with 2g of acetone. The flask temperature was then raised again to 50° C. andheld at 50° C. until NCO % reached 2.0% or less.

With the temperature at 50° C., 570 g of deionized (DI) water was addedover 10 minutes, followed by 38 g EDA (as a 10% solution in water) over5 minutes, via the addition funnel. The mixture was held at 50° C. for 1hr, and then cooled to room temperature.

Acetone (˜122.0 g) was removed under vacuum, leaving a final dispersionof polyurethane with about 30.0% solids by weight.

All PUD type polymers in Table 6 below were made using similarprocesses. The polyurethane PUD EX2 described in U.S. Pat. No. 9,255,207was employed as polyurethane polymer binder PUD-A7.

TABLE 6 Monomer weight PUD-A1 PUD-A2 PUD-A3 PUD-A4 PUD-A5 PUD-A6 IPDI120 205 205 200 220 221.5 DMPA 15.8 27 27 25 21 52 Terathane T650 104.7180 180 300 Eternacoll UC-100 412 TEA 1.1 2.0 1.8 17 14 35 EDA 3.8 6.56.5 1.1 TMP 4.0 7 7 7 6 DETA 8.5 8.5 CHDM 15.8 27 27 85 Ammonia (28%) 12DMEA 14.5

Preparation of Inks

Inks used in the examples were made according to standard procedures inthe inkjet art. Ingredient amounts are in weight percent of the finalink. Polymer binders and colorants are quoted on a solids basis. As anexample of ink preparation, an ink vehicle was prepared and added withstirring to an aqueous ink binder. After stirring until a homogeneousmixture was obtained, the solution was added to a pigment dispersion andmixed until homogeneous again. Inks 1-7 were prepared using ingredientslisted in Table 7 below.

TABLE 7 Ink-1 Ink-2 Ink-3 Ink-4 Ink-5 Ink-6 Ink-7 Ingredients (Wt %,based on total weight of ink) Cyan pigment 3%  3% Magenta pigment 5.5%Yellow pigment  5% Black pigment  6% White pigment 10% PUD-A1  3%  3% 3% 2.5% PUD-A6  5% PUD-A7 6%  5% 1,3 Propanediol 18%  15%  15%  11% 14% 11% 13% 1,2 Propanediol 15%  11% 14%  11% 13% Propylene 7.5% glycoldi-methyl ether Dipropylene 2.5% glycol n-propyl ether Surfynol 4200.5%  0.1%  0.2% 0.2%  0.2% Surfynol 440 0.5%  0.5% 0.5%  0.4% Dynol 980 1% Byk 348 0.25%  DI water Balance to 100%       

Printing

The film used for printing was a primer coated Mylar MLBT from DuPontTeijing Film. The film was coated with a primer, and then printed withan example ink using a lab printing system. In this printing system,inks were jetted from a mounted stationery Fuji (Tokyo, Japan) Samba G3Lprinthead onto the film held to the rotating cylinder underneath. A 1inch by 4 inches solid block with an ink coverage of about 5 g/m² wasprinted. The printed film was subsequently dried at 65° C. for 3minutes. Image quality was rated by a visual color homogeneityassessment, and color OD was measured using an X-Rite Greytag Macbethspectrophotometer. A film without primer coating was printed forcomparison as well. Color of the white ink was reported as opacityinstead of OD. Opacity is equal to 100 times the ratio of the diffusereflectance of a white printed film sample backed by a black body (<0.5%reflectance) to the diffuse reflectance of the same sample backed by awhite body (89% reflectance). For white ink 7, optical density of printsover white tile was 0.78 and optical density of prints over black tilewas 0.45 which resulted in opacity of 57.7.

Opacity=100*[10^(−(density over black tile))/10^(−(density over white tile))]

Image quality was rated as the following,

-   -   Rating 1, excellent color uniformity and coverage    -   Rating 2, uniform color with some white lines due to ink        misdirect or missing jets    -   Rating 3, de-wetting and thicker ink lines on the edge of the        block color

Results of image quality and OD or opacity are shown in Tables 8-10below. The OD of an ink without a primer was not measured due to poorimage quality.

TABLE 8 Ink Ink-1 Ink-1 Ink-1 Ink-1 Ink-2 Ink-2 Ink-3 Primer No Primer-BPrimer-J Primer-K Primer-E Primer-H Primer-E primer Image quality 3 2 12 2 1 1 rating OD NA 1.42 1.63 1.61 1.58 1.63 1.49

TABLE 9 Ink Ink-4 Ink-4 Ink-5 Ink -5 Ink-6 Ink-6 Primer Primer E PrimerH Primer E Primer H Primer E Primer H Image quality 1 1 2 1 1 1 OD 1.481.47 1.16 1.16 2.20 2.15

TABLE 10 Ink Ink-7 Primer Primer H Image quality 1 Opacity 57.5

What is claimed is:
 1. An inkjet ink and primer fluid set comprising: a)an aqueous primer composition comprising a multivalent cation salt and apolymeric binder, wherein said composition forms a coating with a drythickness of from 0.4 to 5.0 micron upon application onto a non-porousplastic substrate, and said coating results in a haze increase of lessthan 10 on said substrate, said multivalent cation salt is present at anamount less than 20 wt %, based on the total weight of the primercomposition, and said polymeric binder is not soluble in water, isstable in the presence of said multivalent cation, and is selected fromthe group consisting of urethane polymer, acrylic polymer and vinylpolymer; b) an aqueous white inkjet ink comprising a titanium oxidepigment dispersion, and a polyurethane binder or an acrylic binder,wherein said titanium oxide pigment dispersion having a particle sizewith D50 in the range of 200 to 350 nm; and c) one or more aqueousnon-white colored inkjet inks, wherein at least one of the inkscomprising a pigment dispersion, and a second polyurethane binder or asecond acrylic binder.
 2. The fluid set of claim 1, wherein said aqueousprimer composition further comprising silica particles.
 3. The fluid setof claim 1, wherein said coating results in a haze increase of less than5 on said substrate.
 4. The fluid set of claim 1, wherein saidpolyurethane binder and said second polyurethane binder are the same. 5.The fluid set of claim 1, wherein said acrylic binder and said secondacrylic binder are the same.
 6. The fluid set of claim 1, wherein saidpolymeric binder is urethane polymer.
 7. The fluid set of claim 1,wherein said polymeric binder is acrylic polymer.
 8. A method ofdigitally printing an image onto a non-porous plastic substratecomprising the steps of: (a) providing an inkjet printer that isresponsive to digital data signals; (b) providing a non-porous plasticsubstrate; (c) applying an aqueous primer composition comprising amultivalent cation salt and a polymeric binder onto the non-porousplastic substrate to form a coating with a dry thickness of from 0.4 to5.0 micron, wherein said coating results in a haze increase of less than10 on said substrate, said multivalent cation salt is present at anamount less than 20 wt %, based on the total weight of the primercomposition, and said polymeric binder is not soluble in water, isstable in the presence of said multivalent cation, and is selected fromthe group consisting of urethane polymer, acrylic polymer and vinylpolymer; (d) loading the printer with an aqueous white inkjet ink andone or more aqueous non-white colored inkjet inks, wherein said whiteinkjet ink comprising a titanium oxide pigment dispersion, and apolyurethane binder or an acrylic binder, said titanium oxide pigmentdispersion having a particle size of D50 in the range of 200 to 350 nm;and wherein at least one of the aqueous non-white colored inkjet inkscomprising a pigment dispersion, and a second-polyurethane binder or asecond acrylic binder; and (e) printing onto the primer coated substrateof step (c) using the white inkjet ink and non-white colored inkjet inksin response to digital signals.
 9. The method of claim 8, wherein saidaqueous primer composition comprising silica particles.
 10. The methodof claim 8, wherein said coating results in a haze increase of less than5 on said substrate.
 11. The method of claim 8, wherein saidpolyurethane binder and said second polyurethane binder are the same.12. The method of claim 8, wherein acrylic binder and said secondacrylic binder are the same.
 13. The method of claim 8, wherein saidpolymeric binder is urethane polymer.
 14. The method of claim 8, whereinsaid polymeric binder is acrylic polymer.
 15. The method of claim 8,wherein said digital signals cause the white inkjet ink to be printedbefore the non-white colored inkjet inks are printed in step (e). 16.The method of claim 8, wherein said digital signals cause the whiteinkjet ink to be printed after the non-white colored inkjet inks areprinted in step (e).